This application claims the priority of German Patent Application No. 197 35 722.9, filed Aug. 18, 1997.
The invention relates to a process and an arrangement for recognizing the rotational direction of an internal-combustion engine using a crankshaft angle sensor, a camshaft angle sensor and an electronic internal-combustion engine control unit which processes signals from the two sensors. The crankshaft angle sensor interacts with a generator gear mounted on the crankshaft and has a plurality of teeth. The camshaft angle sensor interacts with a generator gear mounted on the camshaft and has at least one tooth.
Such a process and such an arrangement are known, for example, from German Patent Document DE 34 31 232 C2. In the case of the arrangement known from German Patent Document DE 34 31 232 C2, the crankshaft angle sensor interacts with a generator gear which is mounted on the crankshaft and has the form of a toothed disk having one hundred twenty (120) teeth of the same size, and the camshaft angle sensor interacts with a generator gear which is mounted on the camshaft and has the form of a lug disk having six teeth of different sizes. By means of the arrangement known from German Patent Document DE 34 31 232 C2, the rotating direction of the internal-combustion engine can be recognized solely by the signal of the camshaft angle sensor. The reason for this is that the sequence of the different length pulses, because of the unequal teeth of the lug disk, differs during a rotation in one direction from the sequence during a rotation in the other direction.
If, however, the camshaft generator gear is provided, for example, only with a tooth in the shape of a semicircular lug (so-called half-segment disk, see FIG. 3), then the rotating direction of the internal-combustion engine cannot be recognized by the sequence of the pulses in the signal of the camshaft angle sensor alone. If the internal-combustion engine carries out a reverse rotation, for example as the result of an engine stall or by rolling backward with the forward gear engaged, and yet the internal-combustion engine control unit assumes that there is a forward rotation of the internal-combustion engine, then, particularly, the ignition and the injection are emitted in an incorrect manner. The problems arising in such a case may include an ignition into the suction system, wet spark plugs, unburnt fuel in the catalyst, an incorrect defect diagnosis or an erroneous deceleration recognition.
It is therefore an object of the invention to permit the rotational direction of the internal-combustion engine to be determined independently of the design of the camshaft generator gear.
This object is achieved by a process and apparatus for recognizing the rotational direction of an internal-combustion engine using a crankshaft angle sensor, a camshaft angle sensor and an electronic internal-combustion engine control unit processing signals from the two sensors. The process assigns a certain first crankshaft position, which can be sensed by the crankshaft angle sensor and exists in the case of a reversely rotating internal-combustion engine, to a certain camshaft position which can be sensed by the camshaft angle sensor. A certain second crankshaft position which exists in the case of a forward-rotating internal-combustion engine is assigned to the same camshaft position. These assignments can be stored in the internal-combustion engine control unit such that they may be queried.
The invention is based on recognizing that, as a result of the tensioning device of the chain drive or belt drive for the camshaft, a defined first position of the camshaft generator gear is obtained with respect to the crankshaft generator gear in the event of a reversely rotating internal-combustion engine. When the internal-combustion engine rotates in a forward direction, as the result of the tensioning device, a defined second position of the camshaft generator gear is obtained with respect to the crankshaft generator gear. This second position differs from the first defined position. According to the invention, the first position is defined by the assignment of a certain camshaft position to a certain first crankshaft position which exists when the internal-combustion engine rotates in a reverse manner, and the second position is defined by the assignment of the same camshaft position to a certain second crankshaft position which exists when the internal-combustion engine rotates in a forward manner. The process for recognizing the rotating direction of the internal-combustion engine is carried out particularly through the use of an electronic internal-combustion engine control unit which processes the signals of the crankshaft angle sensor and of the camshaft angle sensor. This processing can be performed by software in the control unit or by a hardwired control circuit, as well as by some combination of hardware and software.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.